This study examined the impact of prenatal methadone exposure and NAS on infant neurobehavioral outcomes and temperament at one- and four-months. Mothers in methadone maintenance treatment with infants who were (MethTx; N= 25) or were not medicated (MethNoTx; N=16) for NAS symptomatology and a sociodemographically similar comparison sample (Comp; N= 21) participated in a short-term longitudinal study. At one-month, trained evaluators assessed infant reflex, sensory, and social responsiveness using the Neonatal Network Neurobehavioral Scales. At four-months, dyads participated in the Still Face Paradigm, a social interaction task in which maternal responsiveness is withdrawn and reinstated. Mothers completed standardized infant temperament measures at one- and four-months.

MethTx infants had less regulation, poorer quality of movement, and more stress abstinence at one-month than Comp infants. Despite this, concurrent maternal ratings of infant behavior did not differ between groups. At four-months, infants with prenatal methadone exposure smiled and gazed at mothers more frequently during the Still Face paradigm than Comp infants. Maternally-reported infant temperament at four-months differed such that mothers in the MethNoTx group rated their infants as having less distress to limitations, being easier to soothe, and having less negative affect than Comp infants.

Despite difficult behavioral profiles at one-month, infants with prenatal methadone exposure smiled and gazed toward mothers more frequently (but not for longer durations) than non-exposed infants at four-months. This may indicate infant hyper-vigilance toward mother due to inconsistent social interactions at home in infants with prenatal methadone exposure. In spite of this finding, methadone-exposed infants appear to “catch up” behaviorally to their comparison counterparts by four-months likely due to the cessation of withdrawal symptomatology. More longitudinal work needs to be completed to determine if sleeper effects may emerge in methadone-exposed infants due to prenatal exposures, postnatal withdrawal, and/or inadequate postnatal home environments.